Umami - the so-called "fifth taste" (after the western traditional four: sweet, sour, salt and bitter) - is 100 years old this year. It is unlikely, however, that anyone will make an umami-flavoured cake to celebrate. While the word translates from Japanese as "deliciousness", umami is characterised by a satisfyingly meaty, savouriness. There was a birthday party of sorts though; the New Frontiers of Taste Umami Symposium, which was held in San Francisco, saw gourmands and Michelin-starred chefs from around the world gather to discuss the merits of the flavour which, despite being old enough to receive a telegram from the Queen, has only recently started to gain culinary credence in the UK.

The term umami was first coined in 1908 by Kikunae Ikeda, a Japanese scientist who was researching the taste of dashi, a stock made from seaweed and used in many Japanese dishes. Ikeda discovered that the secret to the taste was the presence of high levels of an amino acid called glutamate in the stock, which gives it its unique brothy character. Later it was discovered that other organic compounds - inosinate and guanylate - also produce the umami taste. However, it was Ikeda's discovery of the flavour in glutamate - he subsequently learned how to mass produce this in the form of monosodium glutamate, (MSG) - that laid the groundwork for a theory that wouldn't be scientifically verified until 2000 when the specific umami-sensitive taste buds on the tongue were identified.

The common sources of umami that most of us will be familiar with are Chinese takeaways, snacks and ready meals thickly laced with MSG. In part this is because it enhances other flavours so much that manufacturers can get away with using fewer costly ingredients. But, despite having been repeatedly cleared for human consumption by the US Food and Drugs Administration and classified as safe by the World Health Organisation, MSG has been dogged by health concerns. Recent studies have linked high consumption of it with both retina damage and obesity. So the chefs who are now enthusiastically investigating umami are keen to emphasise the differences between the ingredients that they're working with and MSG. "Monosodium glutamate got a bad press because it was seen as not being natural, whereas umami is a completely natural thing," explains Alexis Gauthier, executive head chef at the Michelin-starred Roussillon restaurant in London. "They're two different things. It's like comparing the natural high you experience when watching the sunset with a loved one with the high you'd get from taking LSD."

Gauthier has a number of umami-rich dishes on his menu such as green asparagus rolled in Parmesan, brown butter and chicken jus, or crispy cured pancetta, purple artichokes, baby onions and confit tomatoes with red-wine vinegar dressing. "It usually only takes the addition of one ingredient such as parmesan or veal jus or grilled bacon," he says. "You know when umami ingredients have been added. There is no word for it but 'exquisite!'"

According to Gauthier, despite the fact that the word 'umami' hasn't been flying around European kitchens much until now, most chefs understood the concept of the flavour, regardless of whether they knew about the science. "Even though it was a Japanese professor who put a name to it, the French have been using foods that are high in umami for centuries, such as veal stock to add flavour to a dish - it just never had a name before. I think the understanding of it is still a relatively new and exciting thing in the UK, unlike places such as New York where diners now go out looking to score umami hits."

It certainly is a sensationally moreish flavour. "I came across it about two or three years ago when I was doing some research into taste for a documentary about umami where we tested how it could be practically used in kitchens," says Chris Horridge, Michelin-starred chef from The Bath Priory. "We made two plates of a red mullet dish and two of a venison dish. They were identical apart from the fact that one from each had a higher umami content - there was extract of mushroom in one and parmesan in another, hidden among the rest of the food. Then we had professional tasters come in to see which version of the dish they preferred. Every single one went for the dishes higher in umami."

Part of the reason why the palate responds so favourably towards glutamate could be our early exposure to it - breast milk has very high levels, 10 times higher than cow's milk. However, as with all good tastes, umami guides our appetites towards foods with optimum nutrition. Just as sweet foods signal that there are sugars in foods, salty tastes indicate the presence of minerals, and sour and bitter tastes keep us away from foods that could potentially poison us, research suggests that umami-rich foods alert us to the presence of proteins.

How did umami avoid detection for so long? The answer, it seems, lies in its subtlety. One of its strengths is in enhancing other flavours in a dish. "Even if you taste monosodium glutamate in its purest form," says Horridge, "it doesn't really taste of anything. The best that you can say is that it makes things seem more "meaty". We do cep breadcrumbs, which are very high in umami, with a grouse dish at the moment, and they are so moreish. It doesn't have to be in your face but your palette picks it up without really registering that flavour."

If you want to experiment with umami in your kitchen at home, you won't have to look hard to find ingredients that can up the glutamate content of your dishes. Research has shown that combining different elements that deliver umami (ie mixing sources of glutamate, inosinate and guanylates) can enhance the flavour of a dish by a factor of eight. Key common ingredients rich in umami include fish, such as sardines (glutamate 280mg/100g and inosinate 193mg/100g) or mackerel (inosinate 215mg/100), meats such cured hams (glutamate 337mg/100g) and vegetables including ripe tomatoes (glutamate 246mg/100g). Sauces such as Bovril, soy sauce and anchovy sauce will all provide over 500mg of glutamate per 100g and parmesan cheese contains small white glutamate crystals, providing about 1200mg/100g. However, when you compare these values with some varieties of kombu (the seaweed used in dashi stocks) which can give up to 3190mg of glutamate per 100g, you can see why it was this particular foodstuff which drew Dr Ikeda's attention, leading to his identification of the ultimate elusive flavour.

· This article was amended on Thursday December 4 2008. Homophone corner: "Part of the reason why the palette responds so favourably towards glutamate could be our early exposure to it ...". This has been corrected